Rifapentine is a promising agent in the treatment of tuberculosis, however in a recent trial the once-weekly regimen of rifapentine and isoniazid had a higher relapse rate than the control regimen of twice-weekly rifampin and isoniazid. This may be due to poor bioavailability of the rifapentine formulation used. But there is growing evidence that HIV infection is associated with the occurrence of rifamycin-resistant tuberculosis and there may be a marked propensity for abnormal pharmacokinetics of antituberculosis drugs in patients with HIV infection. This study will therefore examine the pharmacokinetics of INH and rifamycin in HIV seropositive participants in the Rifapentine Clinical Trial, define INH acetylator status in 2 subgroups of participants in the trial, ascertain the degree of bioavailability of INH, rifapentine or rifampin administered in the trial, and compare the use of urine and blood for pharmacokinetic screening.